1. Field of the Invention
The present invention relates to a filter and in particular a filter arranged between a patient and a ventilator, capable of cleaning respiratory air.
2. Description of the Related Art
The use of ventilators in hospitals and the like treatment facilities is very common in order to aid the patient's respiration or even replace the ordinary respiration of the patient. The patient's lungs are thus connected to a ventilator via hoses forcing air into and out of the lungs. There are commonly two hoses from the ventilator, one for expiratory air and one for inspiratory air. These are usually joined in a Y-connection near the patient.
In order to provide comfort to the patient, the inspiratory air has to be pre-heated, a so called single heat system. Some ventilator systems also have heating on the expiratory limb, so-called dual heat systems.
Further, it has become more and more common to use nebulizers in connection with ventilators for administering medicament to the patient. Nebulizers are capable of aerosolizing medicament, i.e. creating very small droplets that are inspired by the patient, thereby reaching the lungs, where the medicament is further distributed into the body of the patient.
In order to prevent that the ventilator becomes contaminated by viruses and/or bacteria exhaled by the patient, a filter is arranged in the expiratory branch. Often the filter is arranged close to the ventilator, a so-called machine side filter.
The exhaled air contains quite a lot of vapour. In a single heat system this vapour will condensate in the expiratory branch, whereby water traps often are arranged in the branch. However, some vapour reaches the filter and will condense on the patient side of the filter. The condensate will wet the filter material causing the filter to function less adequately. This will cause an increase in resistance in the filter and thus a pressure drop that is negative for the patient.
In order to handle this situation, the applicant of the present patent application has developed a filter having a compartment under the filter element, in which the condensate is collected, whereby it is kept out of contact with the filter element, thereby prolonging the life of the filter.
The dual heat systems have been developed in order to reduce the amount of condensate in the expiratory branch, which condensate could be contaminated and could lead to an increased flow resistance. However, this just moves the problem with condensation. The filter element is capable of letting through the gaseous vapour comprising very tiny droplets, but when the vapour has passed the filter element, it will condense because the expiratory branch on this side of the filter is not heated. Thus, the condensate will enter the filter from this side and wet the filter element, with a reduced function as a consequence.
A further problem is the frequent use of nebulizers for administering medicament to the patient. The very small droplets should be inhaled into the lungs of the patient but a certain amount of the droplets will not be inhaled properly but will instead follow the exhaled air in the expiratory branch. A large amount of these droplets will then eventually be stuck in the filter element, severely affecting the function of the filter by clogging.
Recently a specially designed filter has been released on the market, having a wall or fixed surface facing the inlet of the filter, which surface is covered with an absorbing material. The incoming air is thus forced to deflect around the surface while the heavier medicament droplets get caught on the absorbing material. The design of this filter is however not optimal regarding keeping condensate out of contact with the filter element.
As described a few solutions have been presented to handle certain specific problems regarding filters for ventilators, but there is room for improvements regarding handling all types of problem with one filter concept.